Caenorhabditis elegans ( C. elegans) is a small (about 1 mm long) soil
nematode found in temperate regions and may be handled as a microorganism. Although
C. elegans is a primitive organism it nonetheless shares many of the essential
biological characteristics that are central problems of human biology (1). The
development and function of this diploid organism that has been fully sequenced
(2-4), is encoded by an estimated 17,800 distinct genes. C. elegans is regarded
as a model system to facilitate the purification of low abundant proteins involved
in regulatory protein networks. Our initial investigations are focussed on studying
germ line formation during maturation of C. elegans as a model system for regulatory
and developmental processes in multicellular organisms. In this project we are
studying protein expression patterns of the temperature-sensitive C. elegans
mutant glp-1(e2144) (5). This mutant presents a normal phenotype when grown
at 15 °C. However, when grown at 25 °C formation of germ line cells
is lacking.

Differential proteome analyses (6-8) of the C. elegans mutant grown at different
temperatures were performed and characteristic alterations in protein expression
were observed by 2D-gel electrophoresis (2-DE). The protein extracts (1.5 ml)
contained a total of 4.1 mg protein, each. 2D-gel electophoresis (30 x 23 cm2)
was performed with 15 µl aliquots, applying high resolution conditions
(9). Isoelectric focussing was carried out using a pH gradient ranging from
4 to 10. After staining with silver approx. 3000 spots were detected by computer
assisted image analysis. The protein spots were excised using a picking robot.
From the approx. 100 protein spots that were analyzed and identified by MALDI-TOF
MS up to now, about 15 spots / spot families were found reproducibly different
in abundance. While for many of them the function is still unknown, others are
associated with germ cell function. The major sperm protein, for instance, was
found in high abundance only in the 2-DE gels from the culture grown at 15 °C.
This finding correlates well with normal germ cell development at this temperature.
By contrast, in the culture grown at 25 °C vitellogenins were present in
much higher abundance in the corresponding 2-DE gels than in the gels from the
15 °C culture. This can be explained by the lack of germ cells at 25 °C,
as these proteins after production in the intestine are taken up by the healthy
gonads (10).

Hence, mass spectrometric analyses of in-gel digested proteins and subsequent
data base searches are applicable for the identification of protein candidates
associated with the observed phenotypes. The obtained informations lay the grounds
for detailed biochemical and cell biological investigations for studying regulatory
and developmental processes in multicellular organisms.